Boosters generally perform well in frontal crashes. The Turbo should perform as well as any other model. Unlike carseats with a harness, it is the seatbelt that is doing the restraint for children in boosters. The booster itself is not a safety restraint, it is only an aid to allow the seatbelt to fit and work properly on a child.
You may find some boosters fit your child better than others, or some may work better with the seatbelts in your vehicle. Beyond that, you should pick one based on comfort and features. Used properly, the frontal crash protection should be very good with whichever belt-positioning booster you buy.
Some combination boosters that also have a harness have some issues with the guides for the seatbelts. This is not a safety problem as long as you use them properly. See also:
http://www.car-safety.org/faq.html#Q29 .
Side impact crashes are a different issue. Many boosters have very limited side impact protection. Backless models have almost none at all. A few like the Britax Bodyguard and Jupiter Komfort Kruiser have added protection around the head and torso which can help in a side impact. If your child is seated in an outboard position, this may be another factor in your decision.